The Sleep Heart Health Study (SHHS) was started in 1994 as a multicenter cohort study of the cardiovascular consequences of sleep-disordered breathing (SDB). The study's principal aims are to assess SDB as a risk factor for adverse cardiovascular outcomes, including incident coronary heart disease events, stroke, and hypertension, and accelerated increase in blood pressure with age. The SHHS protocol added an assessment of SDB to ongoing cohort studies of cardiovascular and other diseases. During its first four years (1994-1998), the SHHS was successfully started with full and high quality polysomnography (PSG) data obtained in the home from 6,440 participants. Initial cross-sectional findings show that SDB is common and associated with hypertension and self-reported cardiovascular disease (CVD). The clinical centers are now requesting another five years of support to collect additional endpoints needed for testing primary SHHS hypotheses. Additionally in Years 7-9, PSG will be repeated to further characterize SDB in the participants and to describe the natural history of SDB. This application requests support that will allow Case Western Reserve University to continue to serve as the Polysmongraphy Reading Center for the SHHS. In this capacity, we will: a. Provide centralized training for aspects of SHHS related to the performance and interpretation of sleep studies. b. Provide ongoing technical support to the clinical sites for the performance of sleep studies; c. Provide timely review (for quality and medical alerts) and scoring of all records, generating reports needed for participant feedback and data analysis; d. Participate in on-going quality assurance efforts to maintain high levels of scoring accuracy and reliability; e. Develop, implement and monitor the technical performance of PSGs at clinical the field sites; f. Provide reports on study quality to the Steering Committee and QA Committee; g. Collaborate with other SHHS investigators to assist in protocol development, data analysis, data interpretation, and manuscript preparation. The SHHS has shown that large-scale research on sleep, SDB, and disease risk can be conducted in the community and high quality PSG data can be collected from multiple sites by using centralized and intensive methods for training filed technicians and polysomnologists, and for monitoring data quality. Follow-up of the SHHS cohort will provide reliable and accurate data needed to characterize the cardiovascular consequences of SDB, along with its natural history.